ABSTRACT
Screening for pharmaceutically viable stability from measurements of thermally induced protein unfolding and short-term accelerated stress underpins much molecule design, selection, and formulation in the pharmaceutical biotechnology industry. However, the interrelationships among intrinsic protein conformational stability, thermal denaturation, and pharmaceutical stability are complex. There are few publications in which predictions from thermal unfolding-based screening methods are examined together with pharmaceutically relevant long-term storage stability performance. We have studied eight developable therapeutic IgG molecules under solution conditions optimized for large-scale commercial production and delivery. Thermal unfolding profiles were characterized by differential scanning calorimetry (DSC) and intrinsic fluorescence recorded simultaneously with static light scattering (SLS). These molecules exhibit a variety of thermal unfolding profiles under common reference buffer conditions and under individually optimized formulation conditions. Aggregation profiles by SE-HPLC and bioactivity upon long-term storage at 5, 25, and 40 °C establish that IgG molecules possessing a relatively wide range of conformational stabilities and thermal unfolding profiles can be formulated to achieve pharmaceutically stable drug products. Our data suggest that a formulation design strategy that increases the thermal unfolding temperature of the Fab transition may be a better general approach to improving pharmaceutical storage stability than one focused on increasing Tonset or Tm of the first unfolding transition.
